Binding Preference of PEPR1 and PEPR2 for Pep1-6 Binding Preference of PEPR1 and PEPR2 for Pep1-6.(A) and (B) Competition assay of Pep peptides with 125I1-Y-Pep1 (0.5 nM) for binding to transgenic tobacco cells expressing PEPR1 (A) and PEPR2 (B). Binding Preference of PEPR1 and PEPR2 for Pep1-6.(A) and (B) Competition assay of Pep peptides with 125I1-Y-Pep1 (0.5 nM) for binding to transgenic tobacco cells expressing PEPR1(A) and PEPR2(B). Remaining specific binding of 125I1-Y-Pep1 to cells in the presence of unlabeled competitor peptide (Pep1-6) (10 nM) is indicated as a percentage of specific binding of 125I1-Y-Pep1 to the cells without competitor.(C) and (D) Medium alkalinization of transgenic tobacco cells expressing PEPR1(C) and PEPR2(D) by the Pep peptides, assayed at the five concentrations shown.(E) The effect of Pep peptides on the expression pattern of MPK3 gene for the T-DNA mutants. Two-week-old Arabidopsis seedlings grown in liquid medium were incubated with 10 nM peptide for 30 min, and the expression was analyzed by qRT-PCR. Expression levels are indicated relative to the expression in wild-type seedlings supplied with water.Error bars indicate se for three ([A] to [D]) and five (E) different experiments. The number of asterisks indicates samples that are significantly different from corresponding samples supplied with water ([A], [B], and [E]) and with Pep1 ([C] and [D]) (t test: one asterisk, P < 0.05; two asterisks, P < 0.01; three asterisks, P < 0.001). Yube Yamaguchi et al. Plant Cell 2010;22:508-522 ©2010 by American Society of Plant Biologists